<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    * {
      padding: 0;
      margin: 0;
      box-sizing: border-box;
    }
    .container {
      border: 1px solid red;
      max-width: 960px;
      margin: 15px auto;
      border-radius: 5px;
    }
    .form-group{
      display: flex;
      justify-content: center;
      flex: 1;
    }
    .form-group-label{
      text-align: right;
      flex: 0 0 20%;
      padding: 15px;
    }
    .form-group-input{
      flex: 0 0 80%;
      padding: 10px 10px;
    }
    input[type=password]{
      width: 95%;
      margin-right: 15px;
      border-radius: 8px;
      padding: 10px 15px;
    }
    input[type=text]{
      width: 95%;
      margin-right: 15px;
      border-radius: 8px;
      padding: 10px 15px;
    }
    input[type=radio]{
      margin: 10px 0;
    }
  </style>
</head>
<body>
<div class="container">
  <form>
    <div class="form-group">
      <label class="form-group-label">用户名:</label>
      <div class="form-group-input">
        <input type="text">
      </div>
    </div>
    <div class="form-group">
      <label class="form-group-label">密码:</label>
      <div class="form-group-input">
        <input type="password">
      </div>
    </div>
    <div class="form-group">
      <label class="form-group-label">性别:</label>
      <div class="form-group-input">
        <label><input type="radio" name="sex">男</label>
        <label><input type="radio" name="sex">女</label>
      </div>
    </div>
  </form>
</div>
</body>
</html>